Six points is a lot, especially since they were all from essays. That just goes to show you the "human error" associated with grading essays. Even if the graders have structured criteria that they are required to use when grading, they still have bias and use subjective criteria when grading.

Most re-scoring adjustments come from the essay scoring sections as the graders use very subjective criteria when reviewing and grading essays. There could be scoring adjustments on the multiple choice section if you erased and redid.